1. Field
Apparatus and methods consistent with the present disclosure relate to an electromagnetic wave shielding thin film and a method for forming the same, and more particularly, to an electromagnetic wave shielding thin film having superelasticity and a method for forming the same.
2. Description of the Related Art
The electromagnetic wave shielding technology is normally applied from the two aspects. The first aspect is to prevent electromagnetic waves generated in devices from influencing users. As electronic and communication devices are increasingly used in recent years, there is growing concern and interest in harmful effect of electromagnetic waves, and, as the results of researches on negative influence of the electromagnetic waves on the human being are continuously announced, various electromagnetic wave shielding methods for protecting users' health are developing. The second aspect is to protect devices from electromagnetic waves. Normal electronic devices are provided with main boards having a plurality of chips mounted on a printed circuit board. The electronic circuit of the main board is susceptible to Electro Magnetic Interference (EMI) or Radio Frequency Interference (RFI). Therefore, a shielding structure for blocking interference and protecting circuit parts is utilized, and various structures having an electromagnetic wave shielding function are provided on chips to block interference by emitting electromagnetic waves or radio frequency, and thus prevent malfunction of devices or damages to parts, which may be caused by such interference. The basic principle of the electromagnetic wave shielding is reflecting or absorbing low-impedance magnetic-field waves which are guided waves generated in parts to which voltage is applied through electromagnetic wave shielding material, and the corresponding electromagnetic wave shielding material should have electrical conductivity.
The related-art electromagnetic wave shielding structure is divided into two types of structures in view of materials. The most widely used structure is a shield can which is made of metal. The shield can is mounted to enclose the whole parts and block electromagnetic wave interference between parts or between an interior and an exterior of a device. The shield can is normally made of SUS to reflect electromagnetic waves on a surface, and has a high dielectric constant and thus can block an electromagnetic field very efficiently. The shield can is implemented by using crystalline alloy material such as stainless steel, thereby showing electromagnetic wave shielding performance. As the electronic devices have become thinner and slimmer, there has been an attempt to reduce the thickness and size of the shield can. However, since the elastic limit of the material is about 0.02%, plastic deformation may occur in the shield can due to the use of the shield can when it is manufactured as a thin or slim structure, and the quality of a product may deteriorate and the lifespan of the product may be reduced. Furthermore, when the present material is applied to a flexible electronic device, the shield can may suffer from plastic deformation in a deformation range of the device. In addition, insufficient elasticity of the material may cause a defect when an electronic device is manufactured and assembled. That is, in a mass production process in which the shield can with the same shape is repeatedly produced by a pressing method, deformation passing the elastic limit of material easily occurs, and the shield can may be in contact with inner elements, and thus may cause devices to be out of order and may not block electromagnetic waves.
Another type of electromagnetic wave shielding material is high elasticity composite material in which a polymer matrix is charged with conductive material such as metal powder, carbon nanotube, and graphene. Such high elasticity composite material can live up to the demand for miniaturization and slimness of electronic devices, and has both flexibility and an electromagnetic wave shielding property to be applied to flexible electronic devices. When the high elasticity composite material is combined with material such as polymer to have flexibility, there are problems that the flexibility is low in comparison to pure metal material and a manufacturing process is also complicated in comparison to a forming or processing process of existing metal material. In addition, there is a demand for improvement in distribution technology for distributing conductive material uniformly to show a shielding characteristic.